A good article from the Harvard Business Review blog. I definitely agree.

On the face of it, my zero tolerance approach to grammar errors might seem a little unfair. After all, grammar has nothing to do with job performance, or creativity, or intelligence, right?

Wrong. If it takes someone more than 20 years to notice how to properly use "it’s," then that’s not a learning curve I’m comfortable with. So, even in this hyper-competitive market, I will pass on a great programmer who cannot write.

Grammar signifies more than just a person’s ability to remember high school English. I’ve found that people who make fewer mistakes on a grammar test also make fewer mistakes when they are doing something completely unrelated to writing — like stocking shelves or labeling parts.

In the same vein, programmers who pay attention to how they construct written language also tend to pay a lot more attention to how they code. You see, at its core, code is prose. Great programmers are more than just code monkeys; according to Stanford programming legend Donald Knuth they are "essayists who work with traditional aesthetic and literary forms." The point: programming should be easily understood by real human beings — not just computers.